UNS: Taking Advantage of Metal Interpenetration to Improve the Performance of Conjugated Polymer/Fullerene-Based Photovoltaics

PI：Benjamin J. Schwartz提案编号：1510353太阳代表着地球上最丰富的可持续能源的潜在来源。 使用吸光有机聚合物将光转化为电的太阳能电池-有机光伏（OPV）器件-为可再生电力生产提供了一条潜在的低成本路线。 然而，为了达到与其他太阳能光伏技术同等的水平，有机太阳能电池必须将其功率转换效率提高到目前的10.5%世界纪录。 本项目的目标是将金属纳米颗粒添加到有机太阳能电池的活性层中，以提高太阳能转换效率。 OPV器件的有源层由导电聚合物和纳米结构碳组成。如果金属纳米颗粒在正确的位置，它们将通过一个称为等离子体共振的复杂过程增强光吸收，并最终提高太阳能转换效率。 该项目的一个关键创新是，金属纳米颗粒将在活性层内的精确位置形成，以实现这一过程。 作为与该项目相关的教育活动的一部分，主要研究者参加了一个项目，其中纳米技术主题被带到整个大洛杉矶地区的高中教室，在一系列研究生运行的高中教师研讨会。 该研究生将开发和举办以有机太阳能电池为特色的太阳能工作坊。有机光伏器件制造的一个主要技术挑战是精确控制吸光聚合物（电子供体）和富勒烯（电子受体）的纳米级空间分布，以优化电荷分离和光电流收集。 此外，在器件制造期间可能发生其他复杂因素。 例如，通过热蒸发将导电金属沉积在有机聚合物层的顶部上以用作电接触。假设这些蒸发的金属容易移动通过富勒烯，并在位于聚合物层顶部的任何富勒烯下方留下一层金属纳米颗粒，从而对器件性能产生迄今为止被忽视的意外后果。 初步数据支持这一假设，这项研究的总体目标是确定金属互穿对聚合物基光伏器件性能的影响，然后制定策略，有目的地操纵金属纳米粒子互穿，通过等离子体光学吸收增强来提高器件性能。 在拟议的研究中，实验和计算方法将被用来理解这些过程。顺序处理，其中供体（导电聚合物）和受体（富勒烯）层在单独的步骤中沉积，将用于控制OPV有源层内的垂直富勒烯分布。 透射电子显微镜，结合椭圆偏振仪和中子反射仪，将用于研究金属穿透富勒烯的条件。 这些信息将用于开发合成策略，以控制互穿金属的分布，并最终控制形成的金属纳米颗粒的尺寸和位置。介电常数、等离子体吸收增强和激子猝灭测量将在金属纳米颗粒浸渍的有源层上进行，并且这些基本光电性质测量将与器件性能的总体测量相关，包括太阳能转换效率、外部量子效率和光电流/光电压瞬变。 互补模拟耦合麦克斯韦？的方程与标准的漂移扩散求解器将执行与金属纳米粒子在活性层，以帮助理解和解释这些实验结果。 研究结果将提出有目的的方法，同时提高OPV器件的制造和性能。

PI: Benjamin J. Schwartz Proposal Number: 1510353The sun represents the most abundant potential source of sustainable energy on earth. Solar cells that use light-absorbing organic polymers to convert light to electricity - organic photovoltaic (OPV) devices - offer a potentially low-cost route for renewable electricity production. However, in order to achieve parity with other solar photovoltaic technologies, organic solar cells must increase their power conversion efficiency past the current 10.5% world record. The goal of this project is to add metal nanoparticles into the active layer of the organic solar cell to possibly enhance solar energy conversion efficiency. The active layer of the OPV device consists of the conducting polymer and nanostructured carbon. If the metal nanoparticles are in the right place, they will enhance light absorption, and ultimately solar energy conversion efficiency, through a complex process called plasmonic resonance. A key innovation of this project is that that metal nanoparticles will be formed at precise locations within the active layer to enable this process. As part of the educational activities associated with this project, the principal investigator participates in a program where nanotechnology topics are brought to high school classrooms throughout the greater Los Angeles area in a series of graduate student-run workshops for high school teachers. The graduate student supported by this grant will develop and conduct workshops on solar energy featuring organic solar cells.A major technical challenge with the fabrication of organic photovoltaic devices is to precisely control the nanoscale spatial distribution of the light-absorbing polymer (electron donor) and fullerene (electron acceptor) to optimize charge separation and photocurrent collection. Furthermore, other complicating factors may occur during device fabrication. For example, conductive metals are deposited on the top of the organic polymer layer by thermal evaporation to serve as an electrical contact. It is hypothesized that these evaporated metals easily move through the fullerenes and leave a layer of metal nanopart¬icles underneath any fullerenes that reside at the top of the polymer layer, creating unintended consequences to device performance that have been overlooked to date. Preliminary data supports this hypothesis, and the overall goals of this proposed research are to determine the effects of metal interpenetration on the performance of polymer-based PV devices, and then develop strategies to purposely manipulate metal nanoparticle interpenetration to improve device performance through plasmonic optical absorption enhancement. In the proposed research, experimental and computational approaches will be used to understand these processes. Sequential processing, where the donor (conducting polymer) and acceptor (fullerene) layers are deposited in separate steps, will be used to control the vertical fullerene distribution within the OPV active layer. Transmission electron microscopy, in combination with ellipsometry and neutron reflectometry, will be used to study the conditions by which metals penetrate through fullerenes. This information will be used to develop synthesis strategies to control the distribution of interpenetrated metal, and ultimately the size and position of the metal nanoparticles that are formed. The dielectric constant, plasmonic absorption enhancement, and exciton quenching measurements will performed on the metal nanoparticle impregnated active layer, and these fundamental optoelectronic property measurements will be correlated to overall measurements of device performance, including solar energy conversion efficiency, external quantum efficiency, and photocurrent/photovoltage transients. Complementary simulations that couple full solutions of Maxwell?s equations with standard drift-diffusion solvers will be performed with metal nanoparticles in the active layer to help to understand and interpret these experimental results. The research outcomes will suggest purposeful ways to simultaneously enhance OPV device fabrication and performance.